Theoretical Investigation of Six-Mode Multi/Demultiplexer Based on Fused-Type Multicore Fiber Coupler

A six-mode (LP
₀₁
/LP
₁₁
ab/LP
_21ab
/LP
₀₂
) multi/demultiplexer based on a fused-type multicore fiber coupler is proposed, and the coupling characteristics are investigated. The multi/demultiplex operation is achieved by a phase matching between the desired mode of center core and the LP
₀₁
mode of the outer core in the elongated region of the fused-type multicore fiber coupler. From the numerical results based on the beam propagation method, it is found that the coupling efficiencies between the LP
₀₁
and LP
₁₁
/LP
₂₁
/LP
₀₂
modes are more than -0.1 dB, and the crosstalk is lower than -20 dB at the wavelength of 1550 nm.